Over my many years of shooting high power rifle matches, I've always been interested in barrel life. Talking with folks shooting calibers from 22 up through 30, one thing seems to hold true for barrel life. It applies to barrels that shoot about 1/4th MOA at 100, 1/2 MOA at 600 and 3/4ths MOA at 1000 yards; virtually what the best barrels do for 20 to 30 shot groups. And when peak pressure's about 50,000 CUP (58,000 PSI).
When the powder charge is at bore capacity (no. of grains = bore cross sectional area in mm), barrel life's about 3000 rounds for average bullet weights. Heavier ones somewhat less, lighter ones somewhat more. Increase the charge weight over bore capacity for a given bore diameter by 40% and barrel life gets cut to 1/2 as many rounds; double the charge weight and it drops to 1/4 as many. And higher pressures decrease barrel life; lower ones increase it.
Factory sporter barrels go about twice as many rounds shooting groups 50 to 200 percent larger than those "best" ones. Service rifle barrels shooting 300 to 400 percent larger groups will last three to four times as many rounds. For example, the M1 and M14 service rifle barrels' throat erosion gage would read 10 meaning time to rebarrel at about 10,000 to 11,000 rounds.
Most interesting to me is barrel life for .22 rimfire ones. Match rifle barrels used to last 50 to 60 thousand rounds before accuracy started to drop off. Since the ammo makers changed their priming compound by adding more glass grit to improve manufacture safety and more uniform detonation in the 1980's, barrel life was cut to about half as many rounds.
